Question

What is the full form of the IMZ abbreviation?

• A. Invaginating marginal zone
• B. Involuting marginal zone
• C. Ingression marginal zone
• D. Inducing marginal zone

Hint:

Associate the key cell movements with their definitions:

\textbf{Involute:} A sheet of cells rolls inward. (IMZ in amphibians)
\textbf{Invaginate:} A sheet of cells folds in on itself. (Sea urchin endoderm formation)
\textbf{Ingress:} Individual cells detach and migrate inward. (Sea urchin mesoderm formation) \end{itemize}

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In developmental biology, particularly during amphibian gastrulation, the embryo is divided into several zones. The marginal zone lies between the animal and vegetal poles. IMZ is an abbreviation for a specific part of this zone involved in a key gastrulation movement.

Step 2: Detailed Explanation:
- Gastrulation is the process where the single-layered blastula reorganizes into a three-layered gastrula (ectoderm, mesoderm, endoderm). This involves complex cell movements.
- Involution is a specific type of cell movement where a sheet of cells turns inward and spreads over an internal surface.
- The Involuting Marginal Zone (IMZ) is the band of cells in the amphibian embryo that rolls inward over the dorsal lip of the blastopore during gastrulation. These cells will form the future mesodermal structures like the notochord and somites.
- The other terms refer to different cell movements: {Invagination} is an infolding of a cell sheet, and {ingression} is the migration of individual cells from the surface into the embryo's interior.

Step 3: Final Answer:
The abbreviation IMZ stands for Involuting Marginal Zone, which accurately describes the function of this region during gastrulation. Therefore, option (B) is correct.